The present invention relates generally to equipment utilized and operations performed in conjunction with a subterranean well and, in an embodiment described herein, more particularly provides a well system with casing valves for selective well stimulation and control.
Several systems have been used in the past for selectively fracturing individual zones in a well. In one such system, a coiled tubing string is used to open and close valves in a casing string. In another system, balls are dropped into the casing string and pressure is applied to shift sleeves of valves in the casing string.
It will be appreciated that use of coiled tubing and balls dropped into the casing string obstruct the interior of the casing string. This reduces the flow area available for pumping stimulation fluids into the zone. Where the stimulation fluid includes an abrasive proppant, ball seats will likely be eroded by the fluid flow.
Furthermore, these prior systems do not facilitate convenient use of the valves in subsequent operations, such as during testing and production, in steamflood operations, etc. For example, the coiled tubing operated system requires costly and time-consuming intervention into the well to manipulate the valves, and the ball drop operated systems are either inoperable after the initial stimulation operations are completed, or require intervention into the well.
Therefore, it may be seen that improvements are needed in the art of selectively stimulating and controlling flow in a well.